1. Field of the Invention
The invention presented here relates to a multi-chip-module with a base carrier, on which at least in some areas signal conductor tracks and signal contact surfaces are arranged in a single layer, and with at least one semiconductor component operating in the signal range connected with signal conductor tracks and signal contact surfaces.
2. Description of Related Art
Multi-chip-modules (MCM) in prior art serve for the highly integrated arrangement of semiconductor components operated in the signal range (i.e., computer components, memory components, I-O components, etc.). MCMs of this type comprise very fine structures of conductor tracks and contact surfaces, wherein semiconductor components mostly present in the form of unhoused chips are connected with the contact surfaces. Several of these semiconductor components are arranged on a common base carrier. Within the technology, a series of differing designs of such MCMs exist, mentioned as examples shall be solely the EP 0871222 A2, WO 97/22138, WO 97/20273 and EP 0856888 A2. Multi-chip-modules of this type, for example, are arranged on printed circuit boards and contacted through corresponding supply lines of the printed circuit board. Common to all known MCMs, however, is that they exclusively relate to the combination of digital and/or analogue semiconductor components, which are operated with electric powers in the signal range and which, as a rule, are utilised for the outputting of control signals. The conductor tracks and contact surfaces have a small cross section and can be arranged in a single layer or multiple layers on a suitable carrier material, so that, depending on the case in question, a structure in the sense of an MCM-L, an MCM-C or an MCM-D is present. These types, which are designated in such a manner in the specialist literature, differ from one another with respect to the carrier material and the lateral density of the electrically conductive structure. With these conductor tracks and contact surfaces of small cross section, the desired signal semiconductor components, which can be present as unhoused chips or as xe2x80x9cchip-packed devicesxe2x80x9d or as SMD component, etc., are capable of being contacted. MCMs of this type are also utilised for controlling of semiconductor components with electric powers from a few Watts to some kilowatts, in that electric control signals with a low power are applied to corresponding inputs of these semiconductor components. In the fields of the controlled electric power supply of medium to high power, e.g., in the case of small electric motors, electro-pneumatic modules, motors for machine tools, motors for automobiles and right through to locomotive motors, no complete electric isolation of signal circuit and power circuit has to be present.
In other fields of application, such as in telecommunications, a strict electric isolation of the driving primary circuit from the secondary circuit conducting the electric power is demanded. In such a case, electronic components, such as switching relays, reed relays, etc., are employed which, on the basis of more recent developments, are becoming smaller and smaller in their dimensions.
In particular in the field of small automatic units (small robots, automatic assembly units, etc.), but also, however, in the field of telecommunications, it has proven to be a problem that the electronic structures necessary for the operation of the unit, still have a disruptively large volume and, on the other hand, the operational reliability is limited by the terminals, plugs and other devices for creating electric contact between two structurally independent components.
The present invention is therefore directed toward making available a highly integrated circuit layout in the case of an MCM with a base carrier, on which at least in some areas signal conductor tracks and signal contact surfaces are arranged in a single layer, and with at least one semiconductor component operating in the signal range connected with signal conductor tracks and signal contact surfaces.
This objective is achieved in the case of a multi-chip-module by the fact that, on the base carrier, at least in some areas power conductor tracks and power contact surfaces arranged in a single-layer are provided, at least one power electronics component operating in the power range is provided, which is connected with the at least one power conductor track, at least one power contact surface and at least one signal conductor track, and that the power conductor tracks have a larger cross section that the signal conductor tracks at least on the basis of greater thickness dimensions. The comparison of cross sections preferably shall not refer to the overall cross section of all conductor tracks, but shall be refer to the individual cross section of the respective conductor track.
It is known from the printed circuit board technology to equip a base carrier with a conductive layer and, subsequently by means of photo-lithography, to create a conductor track structure on this carrier, wherein conductors of differing cross sections can be produced by differing conductor track widths. However, this process cannot be transferred to the production of very much smaller and, for this reason, very much more finely structured MCMs. Because of the excessive widening of conductor tracks for the purpose of obtaining a suitable cross section, the high integration on an MCM would not be implementable.
In contrast to this, in accordance with the invention it is proposed to arrange power electronics components, which in the meantime are also available in small format, which are operated with a much higher power than the signal semiconductor components, on one and the same base carrier as the signal control system. This is implemented by conductor tracks with a greater thickness than the respectively thinner signal conductor tracks. By means of this, the power conductor tracks can also be arranged very close together, as a result of which high integration can take place on the common base carrier. In addition, the integration of driving electronics and power electronics on an MCM provides the opportunity to offer the users xe2x80x9cintelligent power electronics componentsxe2x80x9d. Therefore on the same carrier in addition to the conductors with a small cross section, conductors and contact surfaces with a large cross section are present, by means of which the required power electronics components (power semiconductors, relays, etc.) can be contacted. From the zone with the conductors of a small cross section, special conductors lead into the zone with conductors with a large cross section, which are able to transmit the corresponding control signals between the signal semiconductor and the power semiconductors. With this, in the smallest possible space and without any connecting elements susceptible to malfunction, a driving of the power electronics components with signal semiconductors is implemented.
Furthermore, there is the possibility that the at least one signal conductor track leading to a power electronics component essentially seamlessly verges into a power conductor track and/or power contact surface. If the same materials are utilised for the power electronic conductor tracks and the signal conductor tracks, then on the basis of suitable manufacturing methods a tight bond of these conductor tracks is produced, which is superior to all other contacting methods. The control signal therefore can be transmitted to the power electronics components with the utmost precision and without any interference, Connecting elements susceptible to malfunction, such as solder points, are therefore superfluous.
Methods mastered up until now have shown that the ratio of the height of a power conductor track and/or power contact surfaces to the height of a signal conductor track and/or signal contact surface is situated within the range of 2 to 300, preferably in a ratio of 20 to 180. On the basis of such a significant difference it is possible to put much higher powers through the power conductor tracks than through the signal conductor tracks, without a large lateral space being required for different power conductor tracks or power contact surfaces.
In preference, in this context the ratio of conductor cross section of power conductor track and/or power contact surface to the conductor cross section of a signal conductor track may amount to 2 to 1000, in preference 80 to 400. Here too it becomes clear that, on the basis of the enormously enlarged cross section, the power capacity differences of the conductor tracks in the signal range and in the power range can be considerable.
An also preferred ratio of height to width of a power conductor track and/or power contact surface in the case of one embodiment is situated in the range of 0.1 to 10, preferably 1 to 4. By means of a combination of widening and increasing the height of the power conductor track relative to the signal conductor tracks, a compromise is achieved,: which contributes decisively to the high integration on a common base carrier.
In most cases it can be foreseen that at least one power conductor track merges into several power contact surfaces for the purpose of jointly contacting a power electronics component. This signifies, that this conductor track comprises branches (junctions) corresponding to the number of contact surfaces. If the power is distributed over the individual contact surfaces, then these can have a correspondingly smaller cross section.
In order for the MCM to be able to be electrically connected to the outside, in accordance with a further embodiment, signal connection contact surfaces and power connection contact surfaces for a respective external connection are provided, wherein the signal connection contact surfaces and the power connection contact surfaces essentially have the same height. As a result of the same height of these contact surfaces, the layout of the MCM is facilitated, because the contact surfaces additionally can be utilised for the positioning. In the case of correspondingly high contact surfaces, the MCM can be installed head first, so that the components arranged on the base carrier are automatically protected.
Another procedure for the equalisation of the differing heights of signal conductor tracks and power conductor tracks consists in arranging the signal contact surfaces and the power contact surfaces on the side opposite the semiconductor components and power electronics components (reverse side) of the base carrier, wherein the connection contact surfaces are in electrical connection with the opposite side (front side) through the conductor track sections, which pass through the base carrier. On the reverse side of the base carrier, the contact surfaces then can have a relatively low height, independent of the height of the conductor tracks arranged on the front side, wherein the power contact surfaces are designed correspondingly larger. This, however, because of the space conditions prevailing on the reverse side, does not prove to be a disadvantage.
An adequate protection for the power electronics components as well as a relatively flat construction height can be achieved by the value, which results from the height of a power conductor track minus the height of a contact surface in electrical contact with this power conductor track, being the same or greater than the height of the power electronics component contacting this power contact surface. This signifies, that the power conductor tracks protectively surround the electronic components and, because they are higher than them, provide a protection against shocks.
A further important aspect, which is important in the case of an integration of signal circuits and power circuits on an MCM, consists in the adequate heat dissipation. For this purpose it is possible to assure that at least one heat conducting element is provided on the base carrier, which is in a thermally conductive connection with a power electronics component. This heat conducting element then conducts the superfluous beat away from the power electronics component, which thereupon can be dissipated through it in any suitable form.
For this purpose, provisions additionally can favourably be made that at least one heat conducting element is connected with a heat exchanger device. The heat exchanger device then takes care of the corresponding dissipation of the heat in function of the power of the electronics component. Possible as heat exchanger devices are all means in miniature form suitable for this purpose, independent of whether a forced cooling or anything similar is provided. In order to also not excessively burden the front side of the MCM with the heat exchanger equipment, so that a high degree of integration is not impaired by this, it may also be arranged on the reverse side of the base carrier, wherein the heat conducting element passes through the base carrier. The heat conducting element therefore conducts the heat through the base carrier to the heat exchanger device arranged on the reverse side. This has advantages in particular in the case of MCMs installed head first, because the possibly tight installation conditions do not lead to a build-up of beat and because the heat is conducted into regions where an adequate heat exchange can be provided for.
In the case of a variant of the heat exchanger it is foreseen, that it comprises fine cooling ribs with a ratio of height to width of 0.1 to 10, in preference 1 to 4. Cooling ribs of this type are capable of being manufactured in a similar manner as the conductor tracks and therefore they have a relatively large ratio of height to width. This, with relatively small structures, makes it possible to provide very high heat exchange rates.
A further variant consists in the fact that a heat exchanger device is connected with a power electronics component in an immediately thermally conductive manner. A cooling structure of this kind can be directly mounted on the power electronics components by means of correspondingly suitable mans of connection, e.g., a thermally conductive adhesive.
In order to be in a position to assure a standardisation, in accordance with an embodiment provisions are made that the signal contact surfaces and the power contact surfaces are arranged grouped on the base carrier such that the module can be inserted into a standardised base. Here there is also the possibility of grouping the contact surfaces such that bases, which are already present, can be utilised. These then solely have to have suitable contacts at the corresponding points for the connection of the power circuits.
The invention furthermore is related to a method for the manufacture of a multi-chip-module. The method comprises the following steps:
Preparation of a base carrier with signal conductor tracks and signal contact surfaces, deposition of a structured layer, by which at least the signal conductor tracks and signal contact surfaces are essentially covered, except for connection points, and which comprises a negative structure of the power conductor tracks and/or power contact surfaces. Filling in the negative structures by means of a metallisation process for the creation of the power conductor tracks and/or contact power surfaces wherein, at the connection points, a contacting of the signal conductor tracks and/or of the signal contact surfaces and of the power conductor tracks and/or power contact surfaces takes place.
As a result of the separate manufacturing of signal conductor tracks and power conductor tracks, structures with differing heights can be created with relatively simple process steps. The already present signal conductor tracks are covered and, except for suitable contact points, sealed off for the protection from the process steps to follow. The base material used by means of the most differing processes can be equipped with a negative structure, which predetermines the course of the power conductor tracks. In preference, this structure goes right through to the base carrier, so that thereupon a coating of the base carrier in the zone of the negative structure can take place. For the metallisation taking place, also differing processes can be utilised. The structured layer defines the form of the power conductor tracks and corresponding contact surfaces, which are creatable by the metallisation. Thereafter, the structured layer protects the corresponding track and contract structures during the manufacturing process.
In preference, on the base carrier in the zone of the negative structure a conductive adhesive layer can be deposited, which serves as the base for the metallisation process. It is important that an adequate connection between the base carrier and the conductor track structures is produced. This preferably can be implemented by a more expensive adhesive layer, which effects the anchoring in a better manner. The further adhesion is thereupon achievable by means of simple metallisation processes because the adhesive layer possesses a corresponding conductivity.
Favourably, the structured layer can be deposited by means of a photo-lithographic process. Very fine structures with very advantageous ratios of height to width can be manufactured by means of such a process. The designing of conductor tracks and contact surfaces in a shape required is achieved in this manner.
In accordance with a variant of the method, the metallisation process can take place by galvanic deposition of metal. In particular in connection with a conductive adhesive layer, on this layer thereupon the desired structure can be created.
In the case of most applications it will be desirable, that in accordance with a variant, following the metallisation process the structured layer is removed.